This invention relates to improvements in or to an angular velocity sensor for detecting the angular velocity of an object through deflection of a gas flow.
Angular velocity sensors generally called "gas rate sensors" are used in the course adjustment or position control of a ship, an automotive vehicle, etc. Those angular velocity sensors are more resistant to vibrations than gyrocompasses and are capable of detecting the angular velocity of a ship or an automotive vehicle with higher sensitivity and more excellent responsiveness than gyrocompasses.
An angular velocity sensor in general comprises a casing, a sensor body mounted within the casing and including a nozzle and a gas flow sensor composed of thermosensitive elements and a cover covering the opening of the casing and forming part of the wall of a pumping chamber defined within the casing. Such angular velocity sensor operates for detecting the angular velocity of an object in which it is mounted, in such a manner that a gas supplied from the pumping chamber is jetted toward the thermo-sensitive elements through the nozzle. A change in the output of the gas flow sensor which is caused by deflection of the gas stream under the influence of angular velocity movement of the object is detected to thereby determine the angular velocity value.
In a conventional angular velocity sensor, the sensor body is comprised of a cylindrical sleeve, a nozzle piece secured to one end of the sleeve and formed therein with a nozzle hole at a diametrical center thereof and a gas flow sensor holder secured on the other end of the sleeve for holding a gas flow sensor composed of a pair of thermo-sensitive elements arranged symmetrically with respect to the diametrical center of the sleeve. A gas flow jetted toward the thermo-sensitive slements through the nozzle hole is deflected due to external angular velocity movement of an object applied to the angular velocity sensor, which results in a difference between the values of radiant heat of the gas stream sensed by the two thermo-sensitive elements. The resulting outputs of the two thermo-sensitive elements are different from each other by an amount corresponding to the actual angular velocity. The angular velocity of the object is thus detected.
Since, as mentioned above, the angular velocity sensors of this kind are adapted to detect the value of angular velocity applied thereto in response to a fine difference between the gas radiant heat amounts which the two thermo-sensitive elements undergo, a change in the ambient temperature can have a detrimental influence upon the angular velocity detecting action of the angular velocity sensor as a factor of disturbance to deteriorate the detecting accuracy.
Further, if the two thermo-sensitive elements are made of heating wires, the difference in output between the two elements is very small, which necessitates the use of high-gain amplifiers in connection with the elements. Such amplifiers are conventionally placed within the casing. However, since those amplifiers have their performances greatly influenced by the ambient temperature, measures are desired for keeping the amplifiers from the influence of a change in the ambient temperature.